wil6210: fix race between disconnect and Tx NAPI

When disconnecting some CID, corresponded Tx vring get released. During vring
release, all descriptors get freed. It is possible that Tx NAPI working on the same
vring simultaneously. If it happens, descriptor may be double freed.

To protect from the race above, make sure NAPI won't process the same vring.
Introduce 'enabled' flag in the struct vring_tx_data. Proceed with Tx NAPI only if
'enabled' flag set. Prior to Tx vring release, clear this flag and make sure NAPI
get synchronized.

NAPI enablement status protected by wil->mutex, add protection where it was
missing and check for it.

During reset, disconnect all peers first, then proceed with the Rx vring. It allows for
the disconnect flow to observe proper 'wil->status' and correctly notify cfg80211 about
connection status change

Signed-off-by: Vladimir Kondratiev <[e-mail]>
Signed-off-by: John W. Linville <[e-mail]>

drivers/net/wireless/ath/wil6210/cfg80211.c

···
 				    struct net_device *dev, u8 *mac)
 {
 	struct wil6210_priv *wil = wiphy_to_wil(wiphy);
+
+	mutex_lock(&wil->mutex);
 	wil6210_disconnect(wil, mac);
+	mutex_unlock(&wil->mutex);
+
 	return 0;
 }
 

drivers/net/wireless/ath/wil6210/main.c

···
 	struct wil6210_priv *wil = container_of(work,
 			struct wil6210_priv, disconnect_worker);
 
+	mutex_lock(&wil->mutex);
 	_wil6210_disconnect(wil, NULL);
+	mutex_unlock(&wil->mutex);
 }
 
 static void wil_connect_timer_fn(ulong x)
···
 {
 	cancel_work_sync(&wil->disconnect_worker);
 	cancel_work_sync(&wil->fw_error_worker);
+	mutex_lock(&wil->mutex);
 	wil6210_disconnect(wil, NULL);
+	mutex_unlock(&wil->mutex);
 	wmi_event_flush(wil);
 	destroy_workqueue(wil->wmi_wq_conn);
 	destroy_workqueue(wil->wmi_wq);
···
 {
 	int rc;
 
+	WARN_ON(!mutex_is_locked(&wil->mutex));
+
+	cancel_work_sync(&wil->disconnect_worker);
+	wil6210_disconnect(wil, NULL);
+
 	wil->status = 0; /* prevent NAPI from being scheduled */
 	if (test_bit(wil_status_napi_en, &wil->status)) {
 		napi_synchronize(&wil->napi_rx);
-		napi_synchronize(&wil->napi_tx);
 	}
 
 	if (wil->scan_request) {
···
 		cfg80211_scan_done(wil->scan_request, true);
 		wil->scan_request = NULL;
 	}
-
-	cancel_work_sync(&wil->disconnect_worker);
-	wil6210_disconnect(wil, NULL);
 
 	wil6210_disable_irq(wil);
 
···
 	struct net_device *ndev = wil_to_ndev(wil);
 	struct wireless_dev *wdev = wil->wdev;
 	int rc;
+
+	WARN_ON(!mutex_is_locked(&wil->mutex));
 
 	rc = wil_reset(wil);
 	if (rc)
···
 
 static int __wil_down(struct wil6210_priv *wil)
 {
+	WARN_ON(!mutex_is_locked(&wil->mutex));
+
 	clear_bit(wil_status_napi_en, &wil->status);
 	napi_disable(&wil->napi_rx);
 	napi_disable(&wil->napi_tx);

drivers/net/wireless/ath/wil6210/pcie_bus.c

···
 		goto stop_master;
 
 	/* need reset here to obtain MAC */
+	mutex_lock(&wil->mutex);
 	rc = wil_reset(wil);
+	mutex_unlock(&wil->mutex);
 	if (rc)
 		goto release_irq;
 

drivers/net/wireless/ath/wil6210/txrx.c

···
 		struct wmi_vring_cfg_done_event cmd;
 	} __packed reply;
 	struct vring *vring = &wil->vring_tx[id];
+	struct vring_tx_data *txdata = &wil->vring_tx_data[id];
 
 	if (vring->va) {
 		wil_err(wil, "Tx ring [%d] already allocated\n", id);
···
 		goto out;
 	}
 
+	memset(txdata, 0, sizeof(*txdata));
 	vring->size = size;
 	rc = wil_vring_alloc(wil, vring);
 	if (rc)
···
 	}
 	vring->hwtail = le32_to_cpu(reply.cmd.tx_vring_tail_ptr);
 
+	txdata->enabled = 1;
+
 	return 0;
  out_free:
 	wil_vring_free(wil, vring, 1);
···
 {
 	struct vring *vring = &wil->vring_tx[id];
 
+	WARN_ON(!mutex_is_locked(&wil->mutex));
+
 	if (!vring->va)
 		return;
+
+	/* make sure NAPI won't touch this vring */
+	wil->vring_tx_data[id].enabled = 0;
+	if (test_bit(wil_status_napi_en, &wil->status))
+		napi_synchronize(&wil->napi_tx);
 
 	wil_vring_free(wil, vring, 1);
 }
···
 	struct net_device *ndev = wil_to_ndev(wil);
 	struct device *dev = wil_to_dev(wil);
 	struct vring *vring = &wil->vring_tx[ringid];
+	struct vring_tx_data *txdata = &wil->vring_tx_data[ringid];
 	int done = 0;
 	int cid = wil->vring2cid_tid[ringid][0];
 	struct wil_net_stats *stats = &wil->sta[cid].stats;
···
 
 	if (!vring->va) {
 		wil_err(wil, "Tx irq[%d]: vring not initialized\n", ringid);
+		return 0;
+	}
+
+	if (!txdata->enabled) {
+		wil_info(wil, "Tx irq[%d]: vring disabled\n", ringid);
 		return 0;
 	}
 

drivers/net/wireless/ath/wil6210/wil6210.h

···
 	struct wil_ctx *ctx; /* ctx[size] - software context */
 };
 
+/**
+ * Additional data for Tx Vring
+ */
+struct vring_tx_data {
+	int enabled;
+
+};
+
 enum { /* for wil6210_priv.status */
 	wil_status_fwready = 0,
 	wil_status_fwconnecting,
···
 	/* DMA related */
 	struct vring vring_rx;
 	struct vring vring_tx[WIL6210_MAX_TX_RINGS];
+	struct vring_tx_data vring_tx_data[WIL6210_MAX_TX_RINGS];
 	u8 vring2cid_tid[WIL6210_MAX_TX_RINGS][2]; /* [0] - CID, [1] - TID */
 	struct wil_sta_info sta[WIL6210_MAX_CID];
 	/* scan */

drivers/net/wireless/ath/wil6210/wmi.c

···
 
 	wil->sinfo_gen++;
 
+	mutex_lock(&wil->mutex);
 	wil6210_disconnect(wil, evt->bssid);
+	mutex_unlock(&wil->mutex);
 }
 
 static void wmi_evt_notify(struct wil6210_priv *wil, int id, void *d, int len)